The research proposed is designed to characterize the chicken's immune response to a Rous virus - induced tumor in both normal and agammaglobulinemic birds. The cell-mediated immunity will be measured by the in vitro microcytotoxicity test. The occurence of blocking factors in sera from tumor bearing birds will be tested in the in vitro cytotoxicity test. If blocking factors are found in sera from tumor-bearing normal birds but not in sera from agammaglobulinemic tumor-bearing birds then the affect of transferred blocking factors on tumor development in agammaglobulinemic birds will be tested. The immune response to a dibenzanthracene-induced tumor in the WC line of chickens will be characterized so that the tumor system possibly could be used for further study on the cell interaction involved in tumor immunity. Attempts will also be made to elicit macrophage migration inhibition factor from spleen cells of agammaglobulinemic tumor-bearing birds with tumor cell stimulation in vitro and to stimulate macrophage cytotoxicity to tumor cells in this material. Such studies are designed to delineate the mechanisms of macrophage activation in an antibody-free system. It is hoped these experiments will set some ground-work for future investigation on the affects of selected immunodeficiencies in immunotherapy, metastasis and tumor development.